Particulate ammonium nitrate sensitized with a liquid hydrocarbon fuel containing calcium chloride as anti-caking agent



United States Patent 3,368,929 PARTICULATE AMMONIUM NITRATE SENSI- TIZED WITH A LIQUID HYDROCARBON FUEL CONTAINING CALCIUM CHLORIDE AS ANTI-CAKING AGENT Gordon W. Bell, Marion, 111., assignor to Commercial Solvents Corporation, a corporation of Maryland No Drawing. Filed Dec. 28, 1964, Ser. No. 421,695 6 Claims. (Cl. 149-46) This invention relates to a particulate ammonium nitrate composition which is substantially non-caking and substantially free-flowing and is particularly concerned with an ammonium nitrate composition containing calcium chloride.

Ammonium nitrate is hygroscopic. It takes up moisture and the individual particles tend to agglomerate to form lumps; under conditions of high humidity the ammonium nitrate particles tend to form a solid mass. This agglomeration tendency of ammonium nitrate is commonly called caking or setting. For most commercial uses it is desirable that the ammonium nitrate particles be freeflowing, e.g., when used as an explosive.

In accordance with the present invention, the ammonium nitrate particles are mixed with anti-caking amounts of calcium chloride in discrete particle form,'e.g., pellets having a size generally from about 6 to 20 mesh (U.S. Sieve Series) generally for at least about 90% of the particles. The anti-caking amounts are generally from about 0.1 to 10 weight percent and preferably from about 1 to weight percent.

The novel compositions of this invention can be prepared with fertilizer grade as well as with explosive grade ammonium nitrate. Generally, fertilizer grade ammonium nitrate contains various additives or fine particulate coatings added to inhibit caking and to promote free-flowing characteristics of the material. Ammonium nitrate, as referred to herein, is defined as ammonium nitrate containing up to 3 percent of various additives such as clay, wax, diatomaceous earth, chalk, etc., in addition to a moisture content ranging up to about 1 percent. Either the granular or prilled form of the ammonium nitrate is useful in preparing the compositions of this invention.

In preparing explosive compositions, granular ammonium nitrate having a particle size of from about 8 to about 200 mesh can be utilized. The sensitivity of the explosive composition is increased by the use of the smaller mesh sizes. Ammonium nitrate prills having a diameter of from about 0.093 inch to about 0.009 inch are also satisfactory for use in preparing explosive compositions.

A specific embodiment of the present invention is directed to nitrocarbonitrate explosive compositions containing calcium chloride. Nitrocarbonitrate explosive compositions basically include ammonium nitrate (AN) as an oxidizing agent and hydrocarbon oil as a sensitizing agent. Sodium nitrate can be substituted for up to about 50% of the AN. Other additives can be included, for instance, solid carbonaceous material, e.g., powdered coal, which can partially replace the liquid hydrocarbon to provide a desired oxygen balance and anti-caking agents to inhibit caking.

The calcium chloride can be advantageously utilized in nitrocarbonitrate explosive compositions described in copending application Ser. No. 421,644 filed on even date herewith which has been abandoned in favor of continuation application Serial No. 634,070 filed April 25, 1967 incorporated by reference. This application describes explosive compositions having good sensitivity and velocity as Well as a relatively high package density, which can be produced using ammonium nitrate particles having a size from about 8 to 200 mesh (U.S. Sieve Series).

The ammonium nitrate, part of which may be ground in an amount sufiicient to provide the desired sensitivity for the composition, is combined with a normally liquid carbonaceous fuel. Generally, from about 0.1 or 0.5 to 8% by weight of the liquid hydrocarbon is added to the ground ammonium nitrate. The maximum sensitivity for the explosive composition is usually within a preferred range of 1.2 to 3%, depending somewhat on the ammonium nitrate particle size. The liquid hydrocarbon may be of any chemical characteristic, e.g., paraflinic, olefinic, naphthenic, aromatic, saturated or unsaturated. Hydrocarbons which are highly viscous at atmospheric temperatures can be heated to permit preparation of compositions. Preferred liquid hydrocarbons include No. 2 fuel oil and furnace oil which are readily available and which are relatively inexpensive. Other hydrocarbons include kerosene, crude oil and lubricating oil fractions. The liquid hydrocarbon is preferably added immediately after grinding.

A solid carbonaceous fuel, e.g., powdered coal, can be added to the explosive composition in an amount suflicient to adjust the oxygen balance to give maximum power. Generally, from about 0.1 to 10% by weight, preferably about 3 to 8% by weight of a solid fuel can be added. The powdered coal advantageously has a particle size generally from about 20 to 60 mesh for at least about percent of the particles.

In addition to the calcium chloride, one or more antrcaking agents can be added to the compositions of the present invention. The anti-caking agents, however, can be added in amounts which combined with the calcium chloride range from about 0.1 to 5 or 10% by weight, preferably from about 1 to 3.9 weight percent in providing explosive compositions having a package density greater than about 1.09 gm./cc. The anti-caking agents other than the calcium chloride are generally in powdered form to provide a very thin coating. It is believed that calcium chloride performs its anti-caking function by its quality of being more hygroscopic than ammonium nitrate. Other anti-caking agents include inert, solid materials which have been employed heretofore in the ammonium nitrate industry to inhibit caking tendencies, such as clay, barytes, wax, chalk, ground apricot pits, corn starch, kieselguhr, diatomaceous earth, and the like. Powdered clay can be advantageously used in combination with calcium chloride to further enhance the anti-caking characteristics of the compositions without causing an adverse effect on their density.

After addition of the solid carbonaceous material and anti-caking agent to the ammonium nitrate-hydrocarbon oil mixture, the explosive composition can be mixed for a period of time sufiicient to thoroughly mix all the ingredients, e.g., on the order of 3 to 25 minutes or more but the total processing should be completed in 2 hours or less. The mixing of the ammonium nitrate, liquid hydrocarbon, solid carbonaceous material and anti-caking agent may be accomplished in a tumbling action mixer or in a positive action blender.

The explosive composition is advantageously packaged in moisture proof containers, e.g., a container with a vapor barrier, to prevent the calcium chloride deliquescing with atmospheric moisture during storage. It is advantageously packaged in water resistant containers for use in water filled or partially filled bore holes. Containers of the explosive composition may be opened and the contents poured directly into the bore hole as a free-flowing material, if the hole is dry.

The following examples more fully illustrate the present invention but it is not intended that the present invention be limited to the specific proportions, ingredients, etc., thereof.

Examples I and II In these examples, the calcium chloride, powdered coal, fuel oil No. 2 and ammonium nitrate used typically have the following specifications. The calcium chloride is of pelleted grade having a maximum moisture content of 0.3% and a size distribution, U.S. Sieve Series as follows:

The powdered coal has an apparent density of about 0.75 to 0.85 and size distribution, U.S. Sieve Series, as follows:

+101% 10+2015% maximum 20 +6030 to 80% 60 +pan60% maximum.

The fuel oil No. 2 is of the following character:

Flash point (Cleveland Open Cup)140 F. minimum Gravity, A.P.I.30 to 38 Atmospheric distillation:

Initial boiling point--370 to 416 F. End boiling point630 to 675 F. Pour pointl to 0 F. Specific gravity, 60 F./60 P. 0.840 to 0.875 Viscosity at 100 F., Saybolt seconds-33 to 38.

The ground, dense ammonium nitrate (AN) is of a specification as follows:

Apparent bulk density (densimeter), 1.0 gm./cc. Screen analysis, U.S. Sieve Series:

-|-trace, maximum (max.)

10 +35-25%, max.

35 +6035%, max.

60 +10020%, minimum (min.)

100 +20013%, min.

200 +pan2%, min.

The prilled AN (porous AN) is of a specification as follows:

Apparent bulk density, 0.78 to 0.85 gm./ cc. Screen analysis, U.S. Sieve Series:

+80.1% -10 +l240 to 70% -l2 +1625 to 50% -16 +205 to +pan-2%.

Each of compositions Nos. 83 and 87 was not sensitive to a No. 8 blasting cap but was sensitive to 20 grams of US. Military Composition C-4 primer explosive. The ingredients in and the character of each of these explosive compositions are set forth in Table I.

TABLE I Example I HHN: ooo coco 000 00 K Dense AN with a particle density of 1.5 gin/cc. minimum. 1 Porous AN with a particle density of 1.35:1:007 gm./cc.

3 Primed with tetryl, rated at 2 diam. pipe.

4 Primed with tetryl, rated at 3 diam, pipe.

Composition No. 83 is produced in a batch mixer. The whole prilled AN and 73 of the No. 2 fuel oil are placed in the mixer and mixed for one minute. The coal, clay and calcium chloride are then added to the mixer. (Dense AN granules are ground and passed into the mixer.) The remainder of the No. 2 fuel oil is slowly added with the ground AN in the mixer and mixing is continued for 5 minutes after the ground AN is added. Thereafter the composition is dumped into a hopper and packaged. It can be packaged in containers having a vapor barrier, and sufficient strength to permit handling in normal use. Packages sized to fit boreholes are to be vibrated to maximum density before closing. The closure is to be so designed that the vapor barrier is closed to prevent moisture from entering either as a liquid or vapor. Wire ties are normally used for this purpose.

Composition No. 87 provides an easily po'urable explosive composition solely from relatively dense AN particles which composition has good sensitivity and velocity.

Example 111 A free-flowing ammonium nitrate explosive composition is prepared by mixing 93 parts by Weight of porous ammonium nitrate prills having a diameter of from about 0.093 inch to about 0.009 inch, 5 parts by weight of No. 2 fuel oil and 2 parts by weight of essentially the same calcium chloride used in Example I.

It is claimed:

1. Free-flowing ammonium nitrate particulate composition comprising anti-caking amounts of calcium chloride particles having a size from about 6 to 20 mesh (U.S. Sieve Series).

2. The composition of claim 1 wherein the anti-caking amounts are from about 0.1 to 10 weight percent.

3. The composition of claim 2 wherein the composition contains a normally liquid hydrocarbon fuel in an amount sufficient to sensitize the composition for use as an explosive.

4. The composition of claim 3 wherein the fuel is present in an amount from about 0.1 to 8 weight percent.

5. The composition of claim 4 containing from about 0.1 to 10 weight percent of solid carbonaceous fuel.

6. The composition of claim 5 wherein the solid carbonaceous fuel is powdered coal.

References Cited UNITED STATES PATENTS 2,975,046 3/1961 Cooley et a1. l4946 2,719,153 9/1955 Schulz 149l1 XR 2,982,641 5/1961 Dawson et a1. 149-92 XR OTHER REFERENCES Gregory, T. 0: Uses and Applications of Chemicals and Related Materials, Reinhold Publishing Corp., New York, 1939.

CARL D. QUARFORTH, Primary Examiner. BENJAMIN R. PADGETI, Examiner. S. I. LECHERT, JR., Assistant Examiner. 

1. FREE-FLOWING AMMONIUM NITRATE PARTICULATE COMPOSITION COMPRISING ANTI-CAKING AMOUNTS OF CALCIUM CHLORIDE PARTICLES HAVING A SIZE FROM ABOUT 6 TO 20 MESH (U.S. SIEVE SERIES).
 2. THE COMPOSITION OF CLAIM 1 WHEREIN THE ANTI-CAKING AMOUNTS ARE FROM ABOUT 0.1 TO 10 WEIGHT PERCENT.
 3. THE COMPOSITION OF CLAIM 2 WHEREIN THE COMPOSI TION CONTAINS A NORMALLY LIQUID HYDROCARBON FUEL IN AN AMOUNT SUFFICIENT TO SENSITIZE THE COMPOSITION FOR USE AS AN EXPLOSIVE. 